<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script>
        // 定义变量，=号表示把右边值关联左边的变量
        var age = 20;

        age = 21;
        console.log(age);

        var name = "张三";
        console.log(name);
    </script>
</head>
<body>
    
</body>
</html>